CN105604943B - A kind of control method of salt well low pressure natural gas production pressure - Google Patents
A kind of control method of salt well low pressure natural gas production pressure Download PDFInfo
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Abstract
A kind of control method of salt well low pressure natural gas production pressure, it uses cold double-screw compressor in hydrojet, and the air inlet of the compressor is provided with pressure gauge；Isolated form variable-frequency motor drives cold double-screw compressor in hydrojet by lamination around property shaft coupling；PLC automatic control system can be according to the rotating speed of the state modulator isolated form variable-frequency motor shown on pressure gauge；Wherein rate-determining steps are as follows：1) the flowing pressure P in shaft bottom is obtainedS；2) well head open-flow capacity Q is obtained by Pitot tube；3) natural gas actually maximum gas production Q is obtaineds；4) tolerance loss amount Δ Q when considering flow resistance is obtained；5) obtain gas and pressure Δ P is lost from shaft bottom to well head；6) well head largest production pressure P is obtainedjs, and be parameter when PLC automatic control system control isolated form variable-frequency motor is stopped by the design of pressure；The present invention can avoid the generation of hole collapse accident, solve air content in tolerance reduction, the prominent disconnected, gas production of tolerance and increase, pull down the technical problems such as gas.
Description
Technical field
The present invention relates to a kind of natural gas extraction technique, more particularly to a kind of control of salt well low pressure natural gas production pressure
Method.
Background technology
China is to find earliest in the world and one of country using natural gas, and just develops the world in 13rd century of Christian era
Upper first gas field --- artesian well gas field.And the exploitation of the bittern, associated natural gas of artesian well is carried out in Zi Gong area, so far
Closely bimillennial history.Salt industry elder generation dig salt well up to more than 1.3 ten thousand eyes in Zi Gong area using blunt brill technology, add up recovery well
Salt is up to more than 8,000 ten thousand tons, and tap natural gas 340 billion cubic meters.Contain in the fracture reservoir in the region abundant natural
Gas, and with primiparity height, the fast, recovery features of long lifespan of successively decreasing.But with the continuous exploitation of underground gas halogen resource, in stratum
Energy be released, totally, the strata pressure in its main gas production area is less than 0.5MPa to strata pressure, forms salt well low pressure day
Right gas.And salt well low pressure natural gas exploit nearby the production status utilized can not meet modernized big insutry production the needs of,
But we must not believe that salt that gas well gas is exhausted.
The eighties in last century, Zigong Salt Industry technical staff is by groping, putting into practice using L-type piston air compressor to salt well
It is successful and promoted that low pressure natural gas be pressurized gathering production, substantially increases the harvesting of salt well associated natural gas
Rate, the needs of modern industrial production gas are met, have expanded market, improve the economic benefit of enterprise.However, above-mentioned technique
In applied to low pressure natural gas recovery process, also with weak point, it is mainly manifested in：
L-type compressor is used piston to be moved back and forth with certain frequency and realizes that gas aspirates, intensifier discharge, inevitable build-up of pressure
Fluctuation is big.Compressor air inlet end pressure and outlet end pressure are determined by compressor model, can not be changed once model is selected
Become also uncontrollable.There is no well cementation measure and salt well is dug by blunt brill technology, in pit shaft, bore hole is up to 1000 meters, mistake
The frequent change of high negative pressure and pressure, easily trigger hole collapse accident and block gas well, ultimately cause gas production reduction, tolerance
Air content increases, pulls down gas etc. in prominent disconnected, gas production.
Therefore, the problem of how selecting the defeated technique of salt well low-voltage natural gas production of reasonable science, and then improving production environment
As the problem urgently studied.
The content of the invention
The invention aims to solve because supercharging exploitation causes pressure difference in well excessive, and then trigger hole collapse accident
This technical problem, and provide a kind of controlling party for the salt well low pressure natural gas production pressure that can determine largest production pressure
Method.
The present invention solves the technical scheme that technical problem uses：
A kind of control method of salt well low pressure natural gas production pressure, using cold double-screw compressor in hydrojet, the compression
The air inlet of machine is provided with pressure gauge；Isolated form variable-frequency motor drives cold twin-screw in hydrojet to compress by lamination around property shaft coupling
Machine；PLC automatic control system can be according to the rotating speed of the state modulator isolated form variable-frequency motor shown on pressure gauge；Wherein control
Step is as follows：
1) the flowing pressure P in shaft bottom is obtainedS；
2) well head open-flow capacity Q is obtained by Pitot tube；
3) natural gas actually maximum gas production Q is obtaineds；
4) tolerance loss amount Δ Q when considering flow resistance is obtained；
5) obtain gas and pressure Δ P is lost from shaft bottom to well head；
6) well head largest production pressure P is obtainedjs, and be that PLC automatic control system controls isolated form by the design of pressure
Parameter when variable-frequency motor is stopped；
Wherein, in step 1) shaft bottom flowing pressure PS, unit：Pa is to be calculated to obtain according to equation below
Wherein, PwFor well head pressure, can be read from the pressure gauge that well head is set, unit：pa；
γ be well in natural gas relative density, unit：kg/m3, it is a constant；
L is well depth in the middle part of gas-bearing formation, can be obtained from label by well；
TpFor mean temperature in well, unit：K；It can be calculated according to equation below：
DtFor geothermal gradient, unit：M/ DEG C, be a constant；
Z is natural gas Gaseous Z-factor, can be according to gas reduced temperature T in wellrWith gas reduced pressure P in wellrMeter
Calculation value checks in Si Tanding-card hereby deviation factor plate.
Wherein, TrFor gas reduced temperature, unit in well：K, PrFor gas reduced pressure, unit in well：pa；
TcFor the critical-temperature of the gas-liquid transformation of natural gas in well, unit：K；
Wherein, PcFor the critical pressure of the gas-liquid transformation of natural gas in well, unit：pa；
Ps' it is to calculate approximate bottom hole flowing pressure, unit：pa；
As L≤1680m,
Work as L<During 1680m,
Well head open-flow capacity Q, unit in step 2)：m3/ d is to be calculated to obtain according to equation below by Pitot tube,
Wherein, D is well head internal diameter, unit：mm；
H is the difference of Pitot tube gross pressure and static pressure, unit：mm；
T be well head air-flow temperature, unit：K；
The actual maximum gas production Q of natural gas in step 3)s, unit：m3/ d, it is calculated by equation below
Qs=Q μ
Wherein, μ is Gas Productivity utilization rate, span 50%~65%；
Tolerance loss amount Δ Q during consideration flow resistance in step 4), unit, m3/ d is calculated by equation below
Δ Q=Q-Qs
Gas in step 5) loses pressure Δ P, unit pa from shaft bottom to well head, is to obtain by the following method：By Δ Q
Calculated value as abscissa, using Δ P calculated value as ordinate, by the Δ Q values calculated, search Δ on the vertical scale
P respective value.
Well head largest production pressure P in step 6)js, unit：Pa, it is to calculate to obtain by equation below：
Pjs=PS-ΔP
By implementing the above method, closure gas well, finally solves tolerance and subtracts caused by can avoiding hole collapse accident
Less, air content increases, pulls down the technical problems such as gas in the prominent disconnected, gas production of tolerance.
Brief description of the drawings
Fig. 1 is Δ Q and Δ P numerical value corresponding diagram.
Embodiment
The present invention is described in further details below in conjunction with the drawings and specific embodiments.
A kind of control method of salt well low pressure natural gas production pressure, its general idea be by geology residing for salt well,
The actual mouthful condition of production of explaining of gas well is analyzed, and is combined correlation theory calculating and drawn gas well liquid loading when institute energy with practical experience
The largest production pressure born, and as the instruction for the speed governing operation for instructing collecting device motor, to ensuring that gas well is pacified
Vital effect is served entirely.
Winning apparatus includes cold double-screw compressor in isolated form variable-frequency motor, hydrojet, its interval used by the technique
Release variable-frequency motor drives cold double-screw compressor in hydrojet by lamination around property shaft coupling, and the air inlet of the compressor is provided with pressure
Power table.PLC automatic control systems are able to detect that the parameter on pressure gauge simultaneously, and can be according to the state modulator isolated form frequency conversion
The rotating speed of motor.Wherein, production pressure when PLC automatic control system controls the motor to be stopped can lead to following method and obtain
.
It is to calculate the flowing pressure P in shaft bottom respectively that it, which obtains the general idea of above-mentioned production pressure,S, well head open-flow capacity
Q, the actual maximum gas production Q of natural gass, then pass through Q-QsObtain consider flow resistance when tolerance loss amount Δ Q, then by Δ Q with
Δ P numerical value corresponding diagram, as shown in figure 1, obtain gas loses pressure Δ P from shaft bottom to well head, finally use PS- Δ P is given birth to
The maximum pressure P that be can bear during production inside salt welljs, by PLC automatic control system by PjsIt is set as largest production pressure,
And to the real-time monitoring of pressure gauge, and then the rotating speed of isolated form variable-frequency motor is controlled, so as to avoid salt well from being internally formed excessive negative pressure,
Cause the accidents such as hole collapse.
Claims (1)
- A kind of 1. control method of salt well low pressure natural gas production pressure, it is characterised in that：Using cold twin-screw compression in hydrojet Machine, the air inlet of the compressor are provided with pressure gauge；Isolated form variable-frequency motor is driven cold double in hydrojet by lamination around property shaft coupling Helical-lobe compressor；PLC automatic control system can be according to the rotating speed of the state modulator isolated form variable-frequency motor shown on pressure gauge； Wherein rate-determining steps are as follows：1) the flowing pressure P in shaft bottom is obtainedS；2) well head open-flow capacity Q is obtained by Pitot tube；3) natural gas actually maximum gas production Q is obtaineds；4) tolerance loss amount Δ Q when considering flow resistance is obtained；5) obtain gas and pressure Δ P is lost from shaft bottom to well head；6) well head largest production pressure P is obtainedjs, and be that PLC automatic control system controls isolated form frequency conversion by the design of pressure Parameter when motor is stopped；Wherein, in step 1) shaft bottom flowing pressure PS, unit：Pa is to be calculated to obtain according to equation below<mrow> <msub> <mi>P</mi> <mi>S</mi> </msub> <mo>=</mo> <msub> <mi>P</mi> <mi>w</mi> </msub> <mo>&times;</mo> <msup> <mi>e</mi> <mfrac> <mrow> <mn>0.03415</mn> <mi>&gamma;</mi> <mo>&CenterDot;</mo> <mi>L</mi> </mrow> <mrow> <mi>Z</mi> <mo>&CenterDot;</mo> <msub> <mi>T</mi> <mi>p</mi> </msub> </mrow> </mfrac> </msup> </mrow>Wherein, PwFor well head pressure, can be read from the pressure gauge that well head is set, unit：pa；γ be well in natural gas relative density, unit：kg/m3, it is a constant；L is well depth in the middle part of gas-bearing formation, can be obtained from label by well；TpFor mean temperature in well, unit：K；It can be calculated according to equation below：<mrow> <msub> <mi>T</mi> <mi>p</mi> </msub> <mo>=</mo> <mn>18</mn> <mo>+</mo> <mn>273</mn> <mo>+</mo> <mfrac> <mi>L</mi> <mrow> <mn>2</mn> <msub> <mi>D</mi> <mi>t</mi> </msub> </mrow> </mfrac> </mrow>DtFor geothermal gradient, unit：M/ DEG C, be a constant；Z is natural gas Gaseous Z-factor, can be according to gas reduced temperature T in wellrWith gas reduced pressure P in wellrCalculated value Checked in this smooth butyl- card hereby deviation factor plate；Wherein, TrFor gas reduced temperature, unit in well：K, PrFor gas reduced pressure, unit in well：pa；<mrow> <msub> <mi>T</mi> <mi>r</mi> </msub> <mo>=</mo> <mfrac> <msub> <mi>T</mi> <mi>p</mi> </msub> <msub> <mi>T</mi> <mi>c</mi> </msub> </mfrac> </mrow>TcFor the critical-temperature of the gas-liquid transformation of natural gas in well, unit：K；<mrow> <msub> <mi>P</mi> <mi>r</mi> </msub> <mo>=</mo> <mfrac> <mrow> <mo>(</mo> <mrow> <msubsup> <mi>P</mi> <mi>s</mi> <mo>&prime;</mo> </msubsup> <mo>+</mo> <msub> <mi>P</mi> <mi>w</mi> </msub> </mrow> <mo>)</mo> </mrow> <mrow> <mn>2</mn> <msub> <mi>P</mi> <mi>c</mi> </msub> </mrow> </mfrac> </mrow>Wherein, PcFor the critical pressure of the gas-liquid transformation of natural gas in well, unit：pa；Ps' it is to calculate approximate bottom hole flowing pressure, unit：pa；As L >=1680m,As L ＜ 1680m,Well head open-flow capacity Q, unit in step 2)：m3/ d is to be calculated to obtain according to equation below by Pitot tube,<mrow> <mi>Q</mi> <mo>=</mo> <mn>0.233</mn> <msup> <mi>D</mi> <mn>2</mn> </msup> <mo>&CenterDot;</mo> <msqrt> <mfrac> <mn>293</mn> <mi>T</mi> </mfrac> </msqrt> <mo>&CenterDot;</mo> <msqrt> <mfrac> <mi>H</mi> <mi>&gamma;</mi> </mfrac> </msqrt> </mrow> 1Wherein, D is well head internal diameter, unit：mm；H is the difference of Pitot tube gross pressure and static pressure, unit：mm；T be well head air-flow temperature, unit：K；The actual maximum gas production Q of natural gas in step 3)s, unit：m3/ d, it is calculated by equation belowQs=Q μWherein, μ is Gas Productivity utilization rate, span 50%~65%；Tolerance loss amount Δ Q during consideration flow resistance in step 4), unit, m3/ d is calculated by equation belowΔ Q=Q-QsGas in step 5) loses pressure Δ P, unit pa from shaft bottom to well head, is to obtain by the following method：By Δ Q meter Calculation value, using Δ P calculated value as ordinate, by the Δ Q values calculated, searches Δ P's on the vertical scale as abscissa Respective value；Well head largest production pressure P in step 6)js, unit：Pa, it is to calculate to obtain by equation below：Pjs=PS-ΔP。
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Effective date of registration: 20171010 Address after: 643000 Xinyuan Road 27, hi tech Industrial Park, Sichuan, Zigong Applicant after: SICHUAN KAIHONG WATER CONSERVANCY MACHINERY MANUFACTURING CO., LTD. Address before: 643000 Zigong province Sichuan City artesian district osmanthus Street No. 184 Jiuding Bookstore 12 floor of No. 36 Applicant before: ZIGONG JIAYU MACHINERY EQUIPMENT CO., LTD. |
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